There are a number of ink receptive coatings available today for various printing techniques. These include coatings which are selectively receptive to water based, solvent based and/or UV cured inks. However, at the present time there is no coating that is receptive to all three classes of inks to provide a single process for making a universally-printable coated substrate.
For example, labels and other materials are designed to be printed on one side and have a pressure sensitive adhesive on the other side. When the label stock is processed into a final product, one form of ink may be used to apply the company logo and/or address, instructions and other indicia. Another form of ink may be used to apply specific information on an individual label, such as the addressee, delivery instructions and the like. Upon receipt by the addressee, a third indicia is sometimes applied to indicate the time or date of receipt. It is possible that each of the separate incidents of the application of indicia may be done with a different generic type of ink, such as the previously mentioned water-based and solvent-based inks as well as UV cured inks such as UV-Flexographic inks.
Various efforts have been made to use various materials in coating formulations. Commonly owned Dodge et al. U.S. Pat. No. 5,310,591 discloses a transparent image-recording sheet suitable for use in a plain paper copier in which an imageable polymer forms substantially the bulk of the coating, along with a particle component that is necessary for feedability of the plain paper copier image recording sheet. Similar patents are Ali et al. U.S. Pat. No. 5,310,595 and Henry et al. U.S. Pat. No. 5,518,809, also commonly owned.
The use of water based toner receptive core/shell latex compositions has been found to be effective in electrophotographic or xerographic imaging, using a transparent film formed from a core/shell latex polymer and polymeric particles. An antistatic agent is used as well. This system is disclosed in commonly owned Sarkar et al. U.S. Pat. Nos. 5,500,457 and 5,624,747. The particles are needed to impart antifriction characteristics for good feeding.
In printing processes, however, there is a need for a gloss coating that is receptive for inks. Coating glossiness is enhanced if the surface is essentially free of particles, and this also facilitates a smooth transfer of ink to the surface. In addition, it has become desirable to prepare both a gloss side and a matte side of materials on which printing is to be applied, using the various inks as described above. The versatility of a coating that adheres effectively to both sides is an advantage since the coating process can apply an ink receptive coating to both sides of any stock and permit the subsequent use of any kind of ink on either side.
Accordingly it would be of great advantage in the art if a single coating could be provided that would permit water based, solvent based and UV cured inks to adhere to the coating.
It would be another advance in the art if the need for multiple ink receptive coatings for different types of inks could be eliminated.
Another advantage would be to provide an ink receptive coating that could coat substrates for later printing, such that no matter what ink might be selected by the printer at some future time. This coating would permit the coating process to function continuously regardless of the intended end use, and, in fact, without concern for such end use or uses.
Yet another advantage would be to provide a water based coating that eliminates the need for solvent or UV curing capabilities, to permit its use in facilities without those capabilities.
Other advantages will appear hereinafter.